Flywheel



March 21, 3933,

w. E. JOHNSON FLYWHEEL Filed April 22,-1952 FigJ.

Inventow: wil Fri 41 E.Johnson,

His Abtobn e L Patented Mar. 21, 1933 UNITED, STATE-S COMPANY, A conrona'r ron on NEW Yomr Application filed April 22,

The present invention relates to flywheels and the like rotatable members having a plurality of arms or spokes and an outer portion, such as a rim in the case of a flywheel, fastened to the arms or spokes.

Great centrifugal forces are set up 1n members of this character during their rotation, causing expansion of the different parts. As the centrifugal force of a rotated element is easily be seen that in a flywheel the centrifugalforce of the rim is relatively greater than that of the inner portions or spokes. These. forces tend to cause different expansions of the different parts. In a flywheel the centrifugal force acting on the rim tends to cause greater expansion than the centrifugal force acting on the spokes, and unless the rim is free to expand, high bending stresses are set up in the rim portions between adjacent arms, reaching maximum values near the arms.

The object of my invention is to provide an improved construction for flywheels and like rotatable members with the outer portion or rim rigidly secured to the arms or spokes, in which the rim or outer portion is free to expand during rotation.

My invention is based on the physical facts I that the stretch or expansion of a material subject to centrifugal force is proportional to its density or specific weight and inversely. proportional to its modulus. of elasticity; in other words, the expansion of an element rotated about an axis depends upon the ratio in which E represents the modulus of elasticity and p the density of the material forming the element, that is, the expansion or stretch increases with decreasing ratio of Let us now consider twoelements rotated at different radii about an axis of rotation. If the elements are of the same material, it is clear that the element rotated at the larger radius stretches or expands more than that rotated at a smaller radius. The outer element, that is, the element rotating at larger radius, is prevented from freely expanding proportional to the radius of rotation it can brackets 6 welded orsolderedto the rim, as 75 1932. SeriaI 'No 606,892. i

in thec'ase of a flywheel in which the outer .elementor rim is rigidly fastened toithe inner elementslor spokes. Inorder to permit free expansionpof the outer element or rim in a' rotatablemember such as a flywheehlmake s the spokes or inner elements of a material haying a ratio less terialforming the-rims; j

For a'better: understanding of what-Lbe lieve to be novel andmy invention, attention is directedto the following description'and the. claims appended-thereto in connection with the drawing-Which forms a part'of my specification. a 5,

In the drawing, where I have shown by way of example a flywheel, Fig. lris a front ;.view and Fig; 2 a sectional view along lines 27 2 of Fig. 1..

Referring to the drawing, 3 is a hub, fldesignates a plurality of spokesintegrally'united .withthe hub, 5is the rim rigidly fastenedto the spokes by any suitable means, in the present instance shown as comprisingblocks or indicated at 7, and defining ,openmgsinto which endportions of the spokes 4 are inserted. r These end portions are rigidlyjfasg tened to the blocks by meansof bolts 18;"

, -The flywheel so far described-istypical. of

any kind offiywheel'or likerotatable member with the spokes rigidly fastened tothe 1 rim According to my inventionfl make the" spokesor arms ofa metal, suchJ-asQaIuminum bronzeffor example, having a ldWmodulus of elasticity ,but relatively hi gh, density, Whereas the rim or outer portion is made of a materialv such as high grade steel or the like, having a higher modulus of elas'ticity. With;such an arrangement the low modulus of elasticityand the high density of the ma- .terial forming the spokes cause a relatively great expansion during rotation, whereas the higher modulus of elasticity and the lower density of the material forming the rim causes relatively lesser expansion during rotation. In other words, the arrangement is such that the tendency to difierences in ex- :22 if it 7 1,902,505

to a' size somewhat less than that necessary toper'mit free expansion ofthe'rim} In or V der to obtain the additionalexpansion of the spokeswhich is necessary to permit freeexpansion of the rim I make the blocks 6 of proper weight to cause the desired additional expansion. 7 7

With my invention'I have. accomplished a reliable flywheel or like rotating member subject tohi'gh centrifugal forces in which bending stresses set up in the different parts and accordingly the danger of explosion of the member are reducedto a minimum. 4 What I claim as new and desire to scour "by Letters Patent of the United States is:

1. A wheel having a plurality of spokes and a rim fastened thereto, the spokes being a of a material for which the ratio 3 is less than the corresponding ratio'for the mate'- rial forming the rim, E representingthe modulus of elasticity and p the density of the respective materials.

2. A wheel having a hub, a rim, and

means for rigidly fastening the rim to the hub, said means being of a metal for which the ratio is less thanthe corresponding ratio for the metal forming the rim, E repre- 'senting the modulus of elasticity and p the I density of the respective metals.

- 3, A wheel as claimedin clann 1 with mem- 'bers fastened to the outer portions of the spokes for increasing the expansion of the spokes during rotation of the wheel. 3

4. A rotatable member having a hub, an

outer portion, and arms for fastening the outer portion to the hub, the arms being of a metal for which the ratio E is less than the I A corresponding ratio for the metal forming 'the outer portion, E representing the mocluv lus of elasticity and p the density. of the respective metals.

5.JA wheel having a plurality of spokes made of aluminum bronze and a rim rigidly fastened to the spokes and made of high 7 grade steel;

In witness whereof, I have hereunto set my hand.

Winrnrn E. JOHNSON. V 

